1. Field of the Invention
The present invention relates to a lens element mainly used for illumination, an illumination optical apparatus for mainly illuminating a spatial optical modulator, and a projection display apparatus for projecting a large-screen image on a screen by using the illumination optical apparatus, a spatial optical modulator for forming an optical image when a video signal is supplied from an external unit, and a projection lens.
2. Description of the Related Art
Various types of projection display apparatuses respectively using the spatial optical modulator have been known so far as video units for a large screen. Each of these projection display apparatuses enlarges an optical image corresponding to a video signal supplied from an external unit with a projection lens and projects the image on a screen by using a transmission- or reflection-type liquid-crystal panel as a spatial optical modulator, illuminating the liquid-crystal panel with a light source, and forming the optical image on the liquid-crystal panel.
It is necessary for an illumination optical apparatus used for a projection display apparatus to have high uniformities of brightness and color, a high light-utilization efficiency, and a large light output on a light-receiving surface (spatial optical modulator).
A projection display apparatus using two lens arrays is disclosed as means for improving the uniformities of brightness and color (e.g. Japanese Patent Application Laid-Open Nos. Hei 3-111806 and Hei 5-346557). FIG. 26 shows a basic configuration of the projection display apparatus. The white light emitted from a lamp 280 is condensed by a concave reflector 281 to become a luminous flux advancing along and in parallel with an optical axis 288, pass through lens arrays 283, 284 and a field lens 285, and illuminate the display region of a liquid-crystal panel 286. A UV-IR cut filter 282 is used to remove unnecessary and harmful infrared light and ultraviolet light from illumination light. An optical image is formed on the liquid-crystal panel 286, which is enlarged by a projection lens 287 and projected on a screen (not illustrated).
It is generally known that the brightness of a luminous flux condensed by a concave reflector increases at a position closer to its optical axis because the luminous flux density rises and decreases at a portion farther from an optical axis because the density lowers. The lens arrays 283 and 284 are used to improve the brightness irregularity of a luminous flux condensed by a concave reflector. The first lens array 283 and the second lens array 284 are respectively constituted by two-dimensionally arranging a plurality of first lenses 283a and a plurality of second lenses 284a. A luminous flux emitted from the concave reflector 282 is divided into a plurality of micro luminous fluxes and these micro luminous fluxes are led in the superimposing configuration each other so that each micro luminous flux illuminates the entire display region of the liquid-crystal panel 286.
The conventional illumination optical apparatus shown FIG. 26 constituted by combining a concave reflector with two lens arrays completely meets the display uniformity requested for a projection display apparatus but it has the problems described below.
When constituting an illumination optical apparatus with lens arrays, the image of the illuminant of the lamp 280 is formed on the apertures of a plurality of second lenses 284a. This state is schematically shown in FIG. 27. When applying a luminous flux having a large brightness irregularity condensed by the concave reflector 282 to the first lens array 283, plural illuminant images 290 at a position closer to the optical axis where the luminous flux density is higher increase in size and the plural illuminant images 290 at a position farther from the optical axis where the luminous flux density is lower decrease in size. when the aperture of the second lens 284a is smaller than the illuminant images 290 formed there, the light leaking from the aperture results in a loss. When applying a large-enough aperture to the illuminant images 290, the illuminant images 290 decrease in size toward the circumference as shown in FIG. 27. Therefore, the number of unnecessary regions increases, the effective aperture 291 of the second lens array 284 increases, and a projection lens having a large converging angle is required. Increase of a converging angle causes the size of a projection lens to increase and results in increase of the cost. To decrease the irradiation angle of the light used for illumination, it is possible to increase an illumination optical path. However, the interval between the second lens array 284 and the liquid-crystal panel 286 increases and the entire size of a projector increases.
When an illuminant formed by the lamp 280 is small enough, the degree of a problem is low. However, an illuminant formed by a metal halide lamp or xenon lamp actually used for the above purpose has a problem because the illuminant has a size of a certain degree.
A projection display apparatus using a plurality of lamps is disclosed as means for increasing the light output of an illumination luminous flux (e.g. Japanese Patent Application Laid-Open Nos. Hei 6-242397 and Hei 6-265887 and Hei 9-50082). FIG. 28 shows a configuration of the above projection display apparatus.
Parabolic mirrors 303 and 304, UV-IR cut filters 305 and 306, first lens arrays 307 and 308, and second lens arrays 309 and 310 are arranged for a plurality of lamps 301 and 302 respectively. The light emitted from the second lens arrays 309 and 310 is divided into three primary color lights of red, green, and blue by dichroic mirrors 311 and 312 and thereafter, passes through field lenses 318, 319, and 320 and enters their respectively-corresponding liquid-crystal panels 321, 322, and 323. Relay lenses 313 and 314 correct the intensity difference of illumination light due to the difference between the illumination optical path lengths which are the distances between the second lens arrays 309 and 310 on one hand and the liquid-crystal panels 321, 322, and 323 on the other. Moreover, plane mirrors 315, 316, and 317 are arranged to bend the optical path of each color. Primary color lights of red, green, and blue emitted from the liquid-crystal panels 321, 322, and 323 are synthesized by dichroic prism 324 and then, enter a projection lens 325. The projection lens 325 enlarges optical images formed on the liquid-crystal panels 321, 322, and 323 and projects them on a screen (not illustrated).
Vicinities of surfaces of the second lens arrays 309 and 310 are almost conjugate with the pupil surface 326 of the projection lens 325 and the sizes and distribution of a plurality of illuminant images formed on the second lens arrays 309 and 310 are focused on the pupil surface of the projection lens 325. FIG. 29 schematically shows the state of illuminant images 340 and 341 formed on the pupil surface 326 of the projection lens 325. In FIG. 29, broken lines are virtual lines showing outlines of the second lens arrays 309 and 310. The illuminant images 340 and 341 corresponding to lamps 301 and 302 are formed on the pupil surface 326 of the projection lens 325 at both the sides of the optical axis 331 of the projection lens 325.
Vignetting is generally provided in the projection lens 325, in which the circumferential illuminance becomes lower than the central illuminance on a screen. This is because the illuminant images 340 and 341 on the pupil surface 326 of the projection lens 325 cause an eclipse due to vignetting. Therefore, when the luminous characteristics of two lamps 301 and 302 arranged at both the sides of the optical axis 331 are different from each other as shown in FIG. 29, illuminant images contributing to the brightness of the circumference of a screen are different from each other. Therefore, color irregularity occurs in a projected image on a screen. Moreover, if any lamp goes out, the illuminance distribution on the screen becomes irregular.
Furthermore, in the case of the configuration shown in FIG. 28, illumination light is led to the liquid-crystal panel 323 for one of primary color lights by arranging the relay lenses 313 and 314 in an optical path and therefore, an illuminant image formed on the pupil surface 326 of the projection lens 325 is reversed to the optical axis 331. Therefore, if the luminous characteristics of two lamps 301 and 302 are slightly different from each other, the condition of the eclipse of the illuminant image differs in only one color due to the vignetting of the projection lens 325 and resultantly, a large color irregularity occurs in a projected image on a screen.
Furthermore, because increase of the number of lamps causes a converging angle necessary for a projection lens to increase, it results in increase of the cost of the projection lens and increase of a projector in size.
As described above, in the case of a conventional illumination optical apparatus used for a projection display apparatus, it is a problem to obtain a luminous flux having a uniform brightness at a high efficiency without increasing the converging angle of a projection lens. Moreover, it is a problem to obtain an illumination luminous flux having a uniform brightness and a large light output at a high efficiency without being affected by an eclipse of a projection lens when a plurality of lamps are used.
It is an object of a lens element of the present invention to work on a luminous flux mainly condensed by a concave reflector and improve the illumination irregularity of the flux. Moreover, it is another object of an illumination optical apparatus of the present invention to form an illumination luminous flux having a uniform brightness, high efficiency, and large light output suitable to be mainly used for a projection display apparatus. Furthermore, by using the illumination optical apparatus of the present invention, it is possible to provide a projection display apparatus for realizing a bright projected image having less display irregularity.
The present invention of the first invention is a lens element working on an input luminous flux advancing along and substantially in parallel with an optical axis to emit an output luminous flux advancing along and substantially in parallel with the optical axis, comprising: an input-side lens group and an output-side lens group in order from an incoming side, wherein the input-side lens group has a negative power nearby an optical axis of an effective aperture and has a power of substantially zero at the circumference of the effective aperture of the input-side lens group, and the output-side lens group has a positive power nearby the optical axis of an effective aperture and has a power of substantially zero at the circumference of the effective aperture of the output-side lens group.
The present invention of the second invention is a lens element working on divergent light to form an output luminous flux advancing along and substantially in parallel with an optical axis, comprising; an input-side lens group and an output-side lens group in order from the incoming side, wherein the input-side lens group has a power of substantially zero nearby an optical axis of an effective aperture and has a positive power at the circumference of the effective aperture of the input-side lens group, and the output-side lens group has a positive power nearby an optical axis of an effective aperture and has a power of substantially zero at the circumference of the effective aperture of the output-side lens group.
In the case of a lens element of the present invention, the light-receiving-surface illuminance increases toward the optical axis because the input luminous flux density rises toward the optical axis but it decreases toward the circumference against the input luminous flux because the input luminous flux density lowers toward the circumference. Therefore, a high-luminous-flux-density region nearby the optical axis lowers in luminous flux density but a circumferential low-luminous-flux-density region remote from the optical axis improves in luminous flux density. Thus, it is possible to improve the uniformity of a luminous flux having a large brightness irregularity.
The present invention of the 3rd invention is an illumination optical apparatus for illuminating a predetermined region with a luminous flux advancing along and substantially in parallel with an optical axis, comprising: an illuminant; a concave reflector for forming a luminous flux advancing along and substantially in parallel with an optical axis by condensing the light emitted from the illuminant; an input-side lens group into which a luminous flux emitted from the concave reflector comes; and an output-side lens group into which a luminous flux emitted from the input-side lens group comes, wherein the input-side lens group has a negative power nearby an optical axis of an effective aperture and has a power of substantially zero at the circumference of the effective aperture of the input-side lens group, and the output-side lens group has a positive power nearby an optical axis of an effective aperture and has a power of substantially zero at the circumference of the effective aperture of the output-side lens group.
The present invention of the 4th invention is an illumination optical apparatus for illuminating a predetermined region with a luminous flux advancing along and substantially in parallel with an optical axis, comprising: an illuminant; a concave reflector for forming a secondary illuminant by condensing the light emitted from the illuminant; an input-side lens group into which the divergent light emitted from the secondary illuminant comes; and an output-side lens group into which a luminous flux emitted from the input-side lens group comes, wherein the input-side lens group has a power of substantially zero nearby an optical axis of an effective aperture and has a positive power at the circumference of the effective aperture of the input-side lens group, and the output-side lens group has a positive power nearby an optical axis of an effective aperture and has a power of substantially zero at the circumference of the effective aperture of the output-side lens group.
The present invention of the 5th invention is an illumination optical apparatus for illuminating a predetermined region by condensing the lights emitted from a plurality of illuminants, comprising: the illuminants; first condensing means for condensing the lights emitted from the illuminants; light synthesizing means for synthesizing the lights condensed by the first condensing means and emitting the synthesized light in a predetermined direction; second condensing means into which the light emitted from the light synthesizing means comes to emit substantially parallel light; a first lens array constituted with a plurality of lenses to divide the light supplied from the second condensing means into a plurality of luminous fluxes; and a second lens array constituted with a plurality of lenses and into which the light supplied from the first lens array comes, wherein images corresponding to the illuminants are formed on the lenses constituting the second lens array.
The 6th invention of the present invention is an illumination optical apparatus for illuminating a predetermined region by condensing the lights emitted from a plurality of illuminants, comprising: the illuminants; first condensing means for condensing the lights emitted from the illuminants; light synthesizing means for synthesizing the lights condensed by the first condensing means and emitting the synthesized light in a predetermined direction; second condensing means into which the light emitted from the light synthesizing means comes to control the luminous flux densities of incoming light so as to become substantially uniform from the vicinity of an optical axis of an effective aperture toward the circumference and emit substantially parallel light; a first lens array constituted with a plurality of lenses to divide the light supplied from the second condensing means into a plurality of luminous fluxes; a second lens array constituted with a plurality of lenses and into which the light supplied from the first lens array comes, wherein the second condensing means is provided with
(1) an input-side lens having a power of substantially zero nearby an optical axis of an effective aperture and having a positive power at the circumference of the effective aperture, and
(2) an output-side lens having a positive power nearby an optical axis of an effective aperture and having a power of substantially zero at the circumference of the effective aperture, and images corresponding to the illuminants are formed on the lenses constituting the second lens array.
The present invention of the 7th invention is an illumination optical apparatus for illuminating a predetermined region by condensing the lights emitted from a plurality of illuminants, comprising: the illuminants; first condensing means for condensing the lights emitted from a plurality of illuminants; light synthesizing means for synthesizing the lights condensed by the first condensing means and emitting the synthesized light in a predetermined direction; second condensing means into which the light emitted from the light synthesizing means comes to emit substantially parallel light; a first lens array constituted with a plurality of lenses to divide the lights supplied from the second condensing means into a plurality of luminous fluxes; a second lens array constituted with a plurality of lenses and into which the light supplied from the first lens array comes; polarized-light separation means into which the light supplied from the second lens array comes to separate natural light into two linearly polarized lights whose polarization directions are perpendicular to each other; and polarized-light rotation means into which the light supplied from the polarized-light separation means comes to rotate the polarization direction of at least one of the two linearly polarized lights, wherein images corresponding to the illuminants are formed on the lenses constituting the second lens array.
The present invention of the 8th invention is an illumination optical apparatus for illuminating a predetermined region by condensing the lights emitted from a plurality of illuminants, comprising: the illuminants; first condensing means for condensing the lights emitted from a plurality of illuminants; light synthesizing means for synthesizing the lights condensed by the first condensing means and emitting the synthesized light in a predetermined direction; second condensing means into which the light emitted from the light synthesizing means comes to control the luminous flux densities of incoming light so as to become substantially uniform from the vicinity of an optical axis of an effective aperture along the circumference and emit substantially parallel light; a first lens array constituted with a plurality of lenses to divide the light supplied from the second condensing means into a plurality of luminous fluxes; a second lens array constituted with a plurality of lenses and into which the light supplied from the first lens array comes; polarized-light separation means into which the light supplied from the second lens array comes to separate natural light into two linearly polarized lights whose polarization directions are perpendicular to each other; and polarized-light rotation means into which the light supplied from the polarized-light separation means comes rotating the polarization direction of at least one of the two linearly polarized lights, wherein the second condensing means is provided with
(1) an input-side lens having a power of substantially zero nearby an optical axis of an effective aperture and having a positive power at the circumference of the effective aperture, and
(2) an output-side lens having a positive power nearby an optical axis of an effective aperture and having a power of substantially zero at the circumference of the effective aperture, and images corresponding to the illuminants are formed on the lenses constituting the second lens array.
In the case of the illumination optical apparatuses of the above 5th to 8th present invention, it is preferable to set a plane mirror for bending an optical path between the first condensing means and the light synthesizing means.
It is more preferable for the plane mirror to use a cold mirror for passing infrared light and reflecting visible light.
It is preferable for the light synthesizing means to use a reflection prism provided with a plurality of reflection planes.
It is preferable for the light synthesizing means to use a rectangular prism provided with a total-reflection plane.
It is preferable that a plurality of lenses constituting the second lens array is a rectangle having a major axis and a minor axis, a plurality of illuminants is arranged on the same plane substantially parallel with the major axis, and the images of the illuminants are arranged along the major-axis direction.
Moreover, in the case of the illumination optical apparatus of the 7th or 8th present invention, it is preferable for the polarized-light separation means to use a plurality of polarized-light separation prism arrays constituted by arranging a plurality of polarized-light separation prisms respectively provided with a polarized-light separation film in the direction perpendicular to a plane including a plurality of illuminants at a constant pitch.
Furthermore, in the case of the illumination optical apparatus of the 6th or 8th present invention, it is preferable to set a plane mirror for bending an optical path between the input-side lens and the output-side lens.
It is more preferable for the plane mirror to use a cold mirror for passing infrared light and reflecting visible light.
An illumination optical apparatus of the present invention makes it possible to form an illumination luminous flux having a high brightness uniformity by using a lens element and a concave reflector of the present invention without increasing the converging angle of a projection lens. Moreover, when using a plurality of lamps, it is possible to form the illuminant images of the lamps on the same lens array and form an illumination luminous flux having a uniform brightness and a large light output at a high efficiency. By arranging polarized-light separation means and polarized-light rotation means at the outgoing side of a lens array, it is possible to form an illumination luminous flux with well-arranged polarization directions.
The present invention of the 16th invention is a projection display apparatus comprising: an illumination optical apparatus for forming illumination light according to said 3rd or 4th invention; a spatial optical modulator into which the light supplied from the illumination optical apparatus comes to form an optical image in accordance with a video signal; and projection means for projecting an optical image on the spatial optical modulator onto a screen.
It is preferable that a projection display apparatus of the 16th present invention is provided with a first lens array plate constituted with a plurality of lenses to divide the light emitted from an illumination optical apparatus into a plurality of luminous fluxes and a second lens array plate constituted with a plurality of lenses to receive the light emitted from the first lens array plate, wherein the second lens array makes the luminous fluxes reach the surface of a spatial optical modulator by superimposing the luminous fluxes each other.
The present invention of the 18th invention is a projection display apparatus comprising: the illumination optical apparatus for forming illumination light according to any one of said 5th to 8th inventions; a spatial optical modulator into which the light supplied from the illumination optical apparatus comes to form an optical image in accordance with a video signal, and projection means for projecting an optical image on the spatial optical modulator onto a screen.
The present invention of the 19th invention is a projection display apparatus comprising: the illumination optical apparatus for forming white light as illumination light according to any one of said 5th to 8th present invention; color separation means for separating the white light supplied from the illumination optical apparatus into lights of red, green, and blue components; three spatial optical modulators into which each color light supplied from the color separation means comes to form an optical image in accordance with a video signal; color synthesizing means for synthesizing red, green, and blue lights emitted from the spatial optical modulator, and projection means for projecting an optical image on the spatial optical modulator onto a screen.
The present invention of the 20th invention is a projection display apparatus comprising: the illumination optical apparatus for forming white light as illumination light according to any one of said 5th to 8th inventions; color separation means for separating the white light supplied from the illumination optical apparatus into lights of red, green, and blue components; a polarized-light separation prism into which each color light supplied from the color separation means comes to separate incoming light into two lights having polarized-light directions perpendicular to each other; three spatial optical modulators into which the light supplied from the polarized-light separation prism comes to form an optical image in accordance with a video signal; color synthesizing means for synthesizing red, green, and blue lights incoming after the red, green, and blue lights emitted from the spatial optical modulators pass the polarized-light separation prism, and projection means for projecting an optical image on the spatial optical modulator onto a screen.
A projection display apparatus of the present invention makes it possible to realize a bright projected image having a high display uniformity with a relatively small projector because of illuminating a spatial optical modulator with an illumination luminous flux formed by an illumination optical apparatus of the present invention and projecting the modulator with a projection lens.